This invention relates to a magneto for a motor vehicle, and more specifically to an assembly of such a magneto in which magnet elements are solidly secured to the inner peripheral surface of the rim of a tray-shaped flywheel.
Generally, magnetos for motorcycles are built so that a set of permanent magnet elements disposed on the inner peripheral surface of a flywheel is rotated and the rapid changes in flux thereby induced in the armature are utilized in generating energy output.
Flywheels for such magnetos in wide use include those (1) based on aluminum in which magnet elements are embedded, (2) made of iron, with magnet elements disposed on the inner peripheral surface of the flywheel rim and fastened thereto by screws from the outside, or (3) made of iron, with magnet elements on the inner peripheral surface of the flywheel rim encased in a casing of nonmagnetic material such as plastics and then secured to the inner peripheral surface.
Of those conventional flywheels, the type (1) provides practically perfect protection for the magnet elements but, being cast in most cases, it has been undesirable because of poor machinability and high material cost.
The type (2), in which magnet elements are screwed to the iron flywheel rim, requires much time in the screwing with an adverse effect on the assembly efficiency. The type (3) that uses encased magnet elements makes it necessary to fabricate the plastic casing separately and then attach the casing to the inner peripheral surface of the flywheel rim, again at a sacrifice of the production efficiency of magneto manufacture. U.S. Pat. No. 3,258,623 teaches another method of fixing magnet elements in palce. However, it does not attempt at thinning the pole pieces or increasing the thickness of the magnet elements, and therefore fails to improve the output capacity. In addition, it too depends on screws for the fixing of elements, with no improvement in productivity.